Magneto ignition system for



Oct. 7, 1952 MACKAY 2,612,886

MAGNETO IGNITION SYSTEM FOR INTERNAL-COMBUSTION ENGINES Filed June 21, 1949 Patentecl Oct. 7, 1952 MAGNETO IGNITION SYSTEM FOR INTERNAL-COMBUSTION ENGINES Eric Glen Mackay, Hawthorn, Victoria, Australia Application June 21, 1949, Serial No. 100,466

In Australia August 5, 1948 like, especially slow starting aircraft and other multi-cylinder engines which are adapted to operate at relatively high speed. More particularly the invention concerns that type of magneto ignition system which includes a battery or the like to provide a supplementary source of current.

The advantage of battery ignition over magneto ignition for starting purposes and of magneto ignition for high speed are well recognised but when the two systems are combined, difiiculties are encountered in that the uni-directional battery current opposes one half cycle of the alternating magneto current. Consequently after starting the engine it has been necessary to cut off promptly the battery current either manually or by means of a suitable automatic switch device.

Another serious disadvantage in such known combination ignition systems is that the alternate opposition to the flux in the core of the magneto induction coil tends to demagnetise or at least materially reduce the effective strength of the usual permanent magnets of the magneto.

The primary object of the present invention is to provide an improved magneto ignition system of the type incorporating a booster battery or the like and which is adapted to furnish an effective supply of current for starting purposes as well as when the engine is running at high speed without having to cut off the supply of battery current. The latter is thus utilized to supplement that of the magneto and enables the weight, size and cost of the system to be materially reduced.

In addition, the permanent magnets of the magneto are maintained in a substantially fully magnetized condition as desired whilst at high speeds any excess current from the magneto is absorbed by the battery.

Referring to the drawings which form part of this specification:

Figure 1 is a diagrammatic view of the improved magneto ignition system in accordance with one embodiment of the present invention.

Figure 2 is a view similar to Figure l of a modification.

Figure 3 is a part sectional, side elevation of a magneto in accordance with one embodiment'of the present invention.

Figure 4 is a wiring diagram showing a polar inductor type of magneto included in the improved ignition system.

The improved ignition system includes any suit- 12 Claims. (Cl. 123-148) able type of magneto having an induction coil 2 provided with primary and. secondary windings 3 and 4 respectively and a battery 6 or any other suitable source of direct current which is wired in circuit with the primary winding as hereinafter described.

Means for making and breaking the battery current are also provided and such means preferably consists of a pair of relatively reciprocatory contacts or the like I. A driven cam 8 having any suitable number of lobes is provided for actuating the contacts which preferably have a condenser 9 associated therewith to minimize sparking.

Hitherto, a single primary winding has been included in the magneto induction coil but in accordance with the present invention, the primary winding includes at least two sections. As seen in Figure 1, two separate primary coils 3a may be provided. These coils are preferably wound in longitudinally spaced relationship on the core ll instead of in overlying relationship so as to ensure the provision of substantially matched coils and prevent undesirable interference therebetween.

One pole I 2 of the battery is connected through the contacts -1 to one end of each primary coil whilst the other end of each primary coil and the other pole l3 of the battery are connected to earth as hereinafter described.

Associated with the foregoing are circuit changing means for alternately including the sections of the primary winding in the common battery circuit in such a manner that the battery current flows first in one direction in one of the primary coils 3a and thence in the opposite direction in the other primary coil to thereby alternately reverse the battery current flux in the induction coil and induce the equivalent of an alternating current in the secondary winding 4.

For this purpose, one pole l2 of the battery is connected by leads l6 either to the adjacent ends of the primary coils 3a as shown or to the opposite ends thereof and the return leads ll of the primary coils are connected to said circuit changingmeans. A rotary switch lever such as a commutator I8 is preferably employed for this purpose as it is particularly suitable for high speed work.

In the embodiment shown, the number of commutator segments 19 correspond to the number of poles in the magneto and the return lead from one coil is connected to alternate segments whilst the return lead'from the other coil is connected to the intervening segments for alternatively reversing the battery current flux in the induction coil as aforesaid.

If desired, the commutator brush 2| and the cam 8 of the contact breaker points 1 may be carried by the magneto armature shaft or any other common shaft and thus rotate at the same speed. For convenience of illustration, they are shown as mounted upon separate-shafts 22, 23 geared together as at 24 so as to rotate at the same speed. In this case, the number of cam lobes correspond with the number of commutator segments employed. The arrangement is such that the maker and breaker contacts 7 are open when the brush 2| is crossing the gap between adjacent segments. Undesirable burning of the segments is thus eifectively eliminated.

The movements of tacts and the commutator are synchronized so that the battery current flow is directed alternately first to one primary coil 3a and then to the other primary coil which is connected electrically opposite so that the current flows in the respective coils in opposite directions for example from the inner to the outer end of each coil. The flux resulting from the unidirectional battery current is thus substantially matched with the alternating flux of the magneto in the induction coil.

It is believed that the primary current is maintained substantially constant at all engine speeds in that during slow running, the magneto current is supplemented by the battery whilst high speed requirements are effectively met by the magneto.

When the magneto current exceeds that of the battery, the excess current is necessarily diverted to the battery. Uncontrolled magnetos, strong enough to spark at very low R. P. M. such for example as 60 R. P. M. are prone to burn excessively the spark plug points at higher speed.

According to a modification as illustrated in Figure 2, the usual single primary winding instead of a pair of separate coils is employed. In this case, the single coil is provided with a substantially central tap 26 and a common lead 21 for example to the maker and breaker contacts and battery in order to electrically divide the primary coil into two sections 3b. The opposite ends of this common coil are connected to the commutator it? as aforesaid so as to alternately reverse the battery current flux in the induction coil.

A suitable practical embodiment is illustrated in Figure 3 of the drawings. The magneto 28 of any suitable type, is provided with a power driven shaft 29 which is adapted to carry both the cam 8 for the maker and breaker contacts and the brush 2i of the commutator. The commutator segments i9 may be mounted in circumferentially spaced relationship in a sleeve or collar 3! surrounding the shaft and the brush may be slidably accommodated in a transverse slot 32 in the shaft.

The brush is spring influenced in any suitable manner. For example, a coiled spring 33 may be mounted in a pocket 34 in the shaft so as to engage one side of an intermediately pivoted lever 36 on the shaft, the opposite end of the lever being adapted to engage the rear of the brush. The spring influence is required mainly when the brush is rotating at relatively low speed. At high speed, centrifugal force ensures efficient contact between the brush and its segments.

The shaft may also be adapted to provide a convenient earth or return lead for the commu the maker and breaker con-- 5921301515. The

' inductor type and the grammatically in Figure 4 of the drawings. In

this case the magneto 28 employed is of the polar primary winding of its inconsists of two matched coils or 0 latter are wired in circuit with a battery 6 through maker and breaker contacts 1 and acommutator or the like 18 as aforesaid.

For convenienc of illustration, the inductor bars 4| are shown mounted on the magneto shaft duction coil 2 shown mounted on separate shafts 42 and 43 respectively. It will be understood however that all of these rotary parts may be mounted upon or actuated by a common shaft if so desired.

Although it is preferred'by reason of control to supplement the magneto current by current from a battery, the supplementary current may be drawn from any other suitable source of direct current such as an electric generator.

When in use on aircraft an important advantage of the improved ignition system is that in the event of the-battery failing, the engine or engines will not cut out but will continue to function on the current supplied solely by the magneto provided that a relay or any other suitable manual or automatic means are employed for earthing the magnetos battery lead.

By the present invention, it is possible to obtain the desired reversal of direct current flow in the primary windings of the induction coil from a single battery. Furthermore, the system enables a common battery current, a common rotary switch device and common maker and breaker means to be employed. The maker and breaker contacts and commutator mechanism are of relatively simple and inexpensive construction and are adapted to function efficiently at high speed whilst the size and weight of the ignition system is reduced to a minimum.

Various alterations, modifications and/or additions may be introduced into the foregoing construction and arrangement of parts without departing from the ambit of the invention as defined by the appended claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A magneto ignition system for internal combustion and like engines comprising a magneto having primary and secondary windings forming an induction coil and a source ofdirect current wired in a circuit with said primary winding which consists of at least two substantially matched sections, circuit changing means for alternately including said sections in the circuit, in such a manner that the direct current flows first in one direction in one of said sections and then in the opposite direction in the other section to thereby alternately reverse the current flux in said induction coil, means for making and breaking the circuit and means for synchronizing the movements of said circuit maker and breaker means and said circuit changing means with the of said sections of the primary winding and amaescv movements of the magneto shaft to thereby substantially match the reversing current flux in said induction coil with the alternating magneto flux therein and thus provide efii'c'ient ignition for engine starting as well as through the rest of the engine speed range without having to cut off the current.

2. A magneto ignition system according to claim 1 wherein the circuit is common to both of said sections of the primary winding and said circuit changing means consists of a common rotary switch device and said circuit maker and breaker means consists of a common pair of relatively reciprocatory contacts having a condenser associated therewith.

3. A magneto ignition system according toclaim 1 wherein said primary winding consists of two separate and substantially identical coils wound in longitudinally spaced relationship upon a common core so as to ensure substantial matching of said coils and minimize undesirable interference therebetween.

4. A magneto ignition system according to claim 1 wherein said primary winding consists of a single coil provided with a substantially central tap connected to a common lead from said circuit so as to electrically divide said primary winding into said sections.

5. A magneto ignition system according to claim 1 wherein the circuit is common to both said circuit changing means consists of a common rotary switch device and said circuit maker and breaker means consists of a common pair of relatively reciprocatory contacts having a condenser associated therewith, said reciprocatory contacts being adapted to be operated by a multi-lobe cam and said .rotary switch device consisting of a commutator the segments of which correspond in number with the lobes on said cam, the brush of said commutator and said cam being mounted on shafts and being adapted to rotate at the same speed.

6. A magneto ignition system according to claim 1 wherein the circuit is common to both of said sections of the primary winding and said circuit changing means consists of a common rotary switch device and said circuit maker and breaker means consists of a common pair of relatively reciprocatory contacts having a condenser associated therewith, said reciprocatory contacts being adapted to be operated by a multi-lobe cam and said rotary switch device consisting of a commutator, the segments of which are less in number than the lobes of said cam, the brush of said commutator and said cam being mounted on separate shafts which are operatively connected together and with the magneto shaft so as to rotate at such synchronized speed that making and breaking of the circuit by said contacts is obtained whilst said brush is traversing each segment and the rotary elements of the magneto are also traversing the induction coil poles.

7. A magneto ignition system according to claim 1 wherein the circuit is common to both of said sections of the primary winding and said circuit changing means consists of a common rotary switch device and said circuit maker and breaker means consists of a common pair of relatively reciprocatory contacts having a condenser associated therewith, said rotary switch device consisting of a commutator the brush of which is mounted on the magneto shaft and with said contacts so that the brush and magneto shaft may rotate at such synchronized speed as to ensure that the rotary elements of the magneto aretraversing the induction coil poles whilst said brush is traversing eachof the commutator segments and saidcontacts are, closed;

8,1-A magneto ignition; system according to claim 1 wherein the circuit is'common to both of said sections of the primary winding and said circuit changing meansconsists of a common rotary switch device, and said circuit maker and-breaker means consists of a common pair of relatively.reciprocatorycontacts having a condenser, associated therewith, said reciprocatory contacts being adapted to be operated by a multilobe cam and said rotary-switch device consisting of a commutator the segments of which correspond in number withthe lobes on said cam, the brush of said commutator and said cam being mounted in longitudinally spaced relationship upon an extension of the magneto shaft around which the segments of said commutator are supported in circumferentially spaced relationship.

9. A magneto ignition system according to claim 1 wherein the circuit is common to both of said sections of the primary winding and said circuit changing means consists of a common rotary switch device and said circuit maker and breaker means consists of a common pair of relatively reciprocatory contacts having a condenser associated therewith, said reciprocatory'contacts being adapted to be operated by a multi-lobe cam and said rotary switch device consisting of a commutator the segments of which correspond in number with the lobes on said cam, the brush of said commutator and said cam being mounted in longitudinally spaced relationship upon an extension of the magneto shaft around which the segments of said commutator are supported in circumferentially spaced relationship, said commutator brush being spring influenced and slidably accommodated in a transverse slot in said magneto shaft.

10. A magneto ignition system accordin to claim 1 wherein the circuit is common to both of said sections of the primary winding and said circuit changing means consists of a common rotary switch device and said circuit maker and breaker means consists of a common pair of relatively reciprocatory contacts having a condenser associated therewith, said reciprocatory contacts being adapted to be operated by a multi-lobe cam and said rotary switch device consisting of a commutator the segments of which correspond in number with the lobes on said earn, the brush of said commutator and said cam being mounted on the same shafts and being adapted to rotate at the same speed, said magneto being of the polar inductor type the inductor bars of which correspond in number with the lobes of said cam and the segments of said commutator.

11. An improved magneto ignition system for internal combustion and like engines comprising a magneto having primary and secondary windings forming an induction coil and a battery source of direct current wired in circuit with said primary winding which consists of two substantially matched sections, a cam operated pair of relatively reciprocatory contacts, and a circuit changing rotary switch device for making and breaking the battery circuit through each of said sections alternately in such a manner that the battery current flows first in one direction in one of said sections and thence in the opposite direction in the other section to thereby alternately reverse the battery current flux in said induction coil, and means for synchronizing the movements of said rotary switch and reciprocatory contacts with the movements of the magneto shaft to thereby substantially match the reversing battery current flux in said induction coil with the alternating magneto flux therein.

12. For use in a magneto ignition system according to claim 1, a magneto having a rotary switch device and apair of cam operable reciprocatory contacts mounted thereon and which are adapted to be wired in circuit with said two sections of the primary winding of the induction coil of said magneto and are adapted to function as the battery circuit changing means and the circuit maker and breaker means.

ERIC GLEN MACKAY.

0 Number REFERENCES CITED The following references are of record in the file of this patent:

UNITEDSTATES PATENTS Name Date 1,026,565 Cunningham May 14, 1912 1,765,454 Schreil June 24, 1930 FOREIGN PATENTS Number Country Date 374,565 France Apr. 20, 1907 475,795 France June 14, 1915 

